The first 'e' causes $str_regexp to be evaluated as Perl code. In other words, it uses the value of $str_regexp as the replacement string. That is compiled along with the rest of the program. There's no risk to this.

The second 'e' causes the content of $str_regexp to be evaluated as Perl code. Since that could have come from anywhere, this is very dangerous.

In reply to Re^4: use qr// variable in right side of s/// operator by ikegami
in thread use qr// variable in right side of s/// operator by psimonovsk

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